In this tutorial review new concepts and experimental results on speech perception, particularly its development, will be described. First, an overview is provided of the results of classical experiments investigating speech preception in its ‘‘initial state.’’ Next, new results demonstrating the effects of language experience on speech preception will be described, showing that the preception of speech is altered by exposure to language in the first 6 months of life. Finally, preception of auditory-visual illusions in speech preception will be described, including a 90-s demonstration experiment that allows audience members to experience the effect. Auditory-visual effects are discussed within the context of speech perception–production links which have their inception in early infancy. A new theory of the development of speech perception that incorporates these results will be presented.